1. Field of the Invention
The invention relates to a detergent sheet of laminate construction useful for the washing of fabrics.
2. The Prior Art
Heavy duty detergent products for laundering of fabrics conventionally have been sold in the form of powders and liquids. Consumers have been required to measure appropriate dosages from containers holding these products. This measuring process sometimes leads to accidental spillage, often is inaccurate, and can generally be described as messy or inconvenient.
Therefore, the industry has sought to overcome these problems by use of a single article containing premeasured amounts of detergent plus other functional cleaning aids within a single package. Two approaches have been taken to providing a single dosage article, namely pouches and impregnated sheets.
Pouches filled with powdered detergents are now presently on the market. These products have some inherent delivery problems. Transfer of the powder actives through the pouch walls is not always sufficiently fast. There are also limits to the amount of product that can be dosed per pouch. By virtue of its construction, the pouch is also bulky and rather large.
Impregnated sheets, on the other hand, have the advantage of being thin. There is also a larger surface area from which the actives can be delivered. This allows greater dissolution rates than available with a pouch. There is no longer a problem of substrate porosity being a limiting factor of construction as in the pouch. Too large a porosity in a pouch will allow powdered product to sieve through during handling. By contrast, sheet articles operate better with large porosity substrates because higher loadings can be achieved. Pouch products also contain trapped air which during the laundry process causes the pouch to float on top of the water surface. This reduces the propensity for contents to dissolve and thereby also delays dosing. Sheets do not suffer from this disadvantage.
There are, however, two significant problems with impregnated single sheets. First, the impregnate detergent formulation must not be overly sticky but rather substantially solid at room temperature. Consumers dislike sheets that feel tacky, wet or greasy. Likewise, the impregnated sheet must have a certain degree of flexibility for ease of use and aesthetic appeal. A boardy hand would not be acceptable. Another disadvantage is the limitation upon amount of the formulation capable of being impregnated into a single sheet. Active detergent loading normally is severely limited by the absorptive capacity of a substrate.
An alternative to the single sheet is a several sheet laminate construction. Lamination sandwiches the detergent formulation between a pair of substrates. This construction avoids the problem with tacky or wet feel and can also achieve higher loadings than the single sheet vehicle. A further advantage is that active systems with up to 30% water can be utilized. This effectively eliminates any need for drying the products.
There are a number of laminated sheet articles reported by the art. U.S. Pat. No. 2,665,528 (Sternfield et al.) discloses a disposable cleaning tissue wherein an adhesive abrasive cleansing mixture is placed between two fibrous substrates. The tissue is intended for re-usable application in cleaning hard surfaces wherein the abrasive mixture slowly released over time. A disadvantage with this construction is that upon complete leaching of the adhesive cleansing medium, the article separates into a pair of substrates which aesthetically detracts from the product.
U.S. Pat. No. 4,170,678 (Urfer et al.) also reports a multiple use article. A layer of fabric softening chemicals is coated both as an outermost and innermost layer of a folded multi-layered flexible substrate. Initially, only the outer coating of fabric conditioner is released to the clothes being tumbled in a clothes dryer. After the first use, the folded article is peeled apart at a loosely-bonded end thereby exposing additional fabric conditioner coated on the inner surface of the article. Similar to impregnated single sheets, this system also features the undesirable aspect of a potentially tacky outer coating. The innermost coating of active material is inhibited from release by attachment of the "free" ends of the folded sheet.
U.S. Pat. No. 4,515,703 (Haq) discloses an article for wiping surfaces comprising two substrate layers bonded together in such a way as to create a plurality of compartments. Within these compartments may be lodged a treating chemical including soap, detergent or bleach. Although this system is described in terms of a laminate construction, in actuality the wiping article is a series of adjoining pouches with all the attendant problems for laundering purposes.
Accordingly, it is an object of this invention to provide a cleaning article in flexible substrate form which when being handled avoids a wet, greasy or tacky feel.
Another object of this invention is to provide a cleaning article which has the capacity to carry a relatively large loading of detergent active material.
Another object of this invention is to provide a cleaning article capable of carrying more than one distinct cleaning composition in physically separate regions of the article.
Still another object of this invention is to provide a cleaning article wherein mutually incompatible compositions of enzyme, bleach, fabric softener and/or detergent are held apart from one another within the article.
It is a further object of this invention to provide a cleaning article which has a substrate that separates into but a single substrate upon exhaustion of the detergent active material therefrom.
It is a still further object of this invention to provide a cleaning article which is simple in its manufacture and convenient to store.
It is an even further object of this invention to provide an effective, convenient product for cleaning clothes in an automatic washing machine.